The present invention relates to a particle separator of the cyclone type for removing particulate solids entrained in a gas stream and particularly relates to a particle separator of the cyclone type intended for separation of solids entrained in flue gases discharged from a circulating fluidized bed reactor.
Many different types of separators, including cyclone separators, have been constructed and used in the past. For example, in Swedish Pat. No. 110,504, there is disclosed a particle separator having a central gas outlet conduit which at one end is in open communication with a cyclone chamber. The outlet conduit is formed at least in part from a plurality of tubes in which a coolant flows. Only a small part of these cooling tubes are in contact with the circulating gases and hence cooling is inefficient.
In British Pat. No. 571,222, there is disclosed a centrifugal dust separator having a casing and an inlet in which dust-laden air is provided to a generally cylindrical chamber having an axially directed outlet. Surrounding the outlet is a plurality of ring deflectors which cause abrupt changes in the direction of the flow of gas entering the outlet. Here, the separator relies on a reduction in pressure to cause the separation of the gas and dust, the deflectors assisting in that regard.
In U.S. Pat. No. 3,470,678, there is disclosed a cyclone separator for use in high temperature operations. In that separator, a plurality of concentric metal tubes are separated one from the other by an annular space in which liquid coolant, in this case steam, is provided. Here, there is no concern evidenced for the temperature condition of the solids extracted from the stream of gas.
It will be appreciated that when adopting a separator of the cyclone type for use with a fluidized bed reactor, efficiency demands recovery of the heat. Concurrently, it is highly desirable that the solid particles removed from the gas return to the reactor at as high a temperature as possible.
According to the present invention, there is provided a particle separator of the cyclone type for removing solids entrained in a hot gas stream, including a cyclone chamber having an axis, together with means for guiding the stream of hot gases with entrained solids about the axis. An inlet duct is provided in communication with the cyclone chamber for introducing the stream into the cyclone chamber in a tangential direction. An outlet is provided adjacent the outer periphery of the cyclone chamber for removing solids separated from the stream.
A particular feature of the present invention resides in the construction of a conduit disposed in the cyclone chamber which extends generally in an axial direction and has a gas outlet. The conduit is formed from a plurality of tubes which extend generally in an axial direction with the tubes adapted to receive a cooling fluid. The tubes further define a plurality of slots therebetween providing for passage of the gas from the cyclone chamber into the conduit and through the gas outlet. Preferably, the tubes and the slots therebetween are arranged to abruptly change the direction of the flow of the gas flowing from the cyclone chamber through the slots into the conduit whereby in addition to centrifugal separation, solids and gases are separated by the inertia of the solids which substantially prevents entry of the solids into the slots and gas outlet conduit. Because the conduit is located generally centrally of the cyclone chamber and, because of the change in flow direction, the solids are efficiently separated from the hot gas stream and the hot separated gases lie in efficient heat exchange relation with the cooling fluid in the tubes.
In one form of the present invention, the tubes have a circular configuration with deflectors projecting generally tangentially of the tubes in the general circumferential direction of the flow of the gases about the cyclone chamber. Slots are formed between the distal ends of the deflectors and adjacent tubes, enabling the gas flow to substantially reverse its direction for flow inwardly toward the central portion of the conduit. In another form, the tubes are formed in a drop shape, with the apex of each drop-shaped tube extending generally tangentially toward the direction of the flow. Thus, the hot gas flows along the outside surface of the drop-shaped tube and then generally reverses its direction for flow along the opposite side of the drop-shaped tube and between it and the adjacent tube. The latter flow is generally radially inwardly into the conduit. In another form, baffles may be provided between a plurality of tubes whereby a plurality of slots are formed, as in contrast to continuous slots. Thus, the gas is efficiently cooled and the heat is recovered in the cooling fluid circulating through the tubes.
The particle separator hereof is particularly useful in conjunction with, and as part of a unitary construction with a fluidized bed reactor, i.e., a steam boiler. Thus, the uptake from the boiler is defined by opposed walls, one of which inclines adjacent the upper end of the uptake toward the opposite wall to define a gas inlet to the cyclone separator located adjacent the upper end of the uptake. Consequently, the gases are injected in a tangential direction into the cyclone separator for flow about an axis, generally coincident with the axis of the tubes forming the gas outlet conduit. The particles separated from the hot gas stream by centrifugal force lie adjacent an outer wall for flow downwardly between the outer wall and the one wall for return to the combustion chamber. Because of the spacing of the outer wall and the location of the cooling tubes generally coincident with the axis of the cyclone chamber, the particulate solids remain hot for return to the reactor.
Separators used in conjunction with fluidized bed reactors are also the subject of my prior U.S. patent applications Ser. Nos. 916,485 and 926,719, filed Sept. 22, 1986 and Nov. 4, 1986, respectively.
Accordingly, it is a primary object of the present invention to provide a novel and improved particle/gas separator having high separating efficiency, a capacity for efficiently cooling the gas and recovering heat therefrom without substantially cooling the separated particles and methods of operating the separator.
It is another object of the present invention to provide novel and improved apparatus and methods for separating particles from hot flue gases from a circulating fluidized bed reactor.
These and other objects and advantages of the present invention will become more apparent upon reference to the following specification, appended claims and drawings.